1. Field of the Invention
The present invention relates to a wet electrophotographic image forming machine and method of use in which developer is supplied in a cartridge type mechanism, and in particular, to a wet electrophotographic image forming machine which is capable of sensing and externally displaying a developer condition allowing the implementation of a method for recognizing a use life of a development cartridge provided therein and informing a user of a replacement need for the development cartridge.
2. Description of the Related Art
In general, a wet electrophotographic image forming machine using a liquid developing agent (hereinafter, referred to as “developer”) forms an image through given electrophotographic image development and transfer processes while continuously maintaining a constant concentration of developer, wherein the concentration is defined as a relative weight ratio between carrier and toner particles indicated by percentage solid.
A description of a developer supplying unit for supplying developer to a photoconductor can be shown by way of an example. A developer supplying unit comprises an enriched developer cartridge containing a developer enriched to have a concentration of 20 to 28% solid, a carrier cartridge containing a solvent for diluting the enriched developer, a developer receptacle for containing developer diluted to a developable concentration (typically achieved by mixing the enriched developer and the carrier, i.e., the solvent), and a concentration sensor and a level sensor for sensing the concentration and remaining amount of the developer contained in the developer receptacle, respectively. In addition, the enriched developer cartridge and the carrier cartridge are also provided with level sensors for sensing remaining amounts of the enriched developer and the carrier, respectively. A waste developer cartridge is also provided for accumulating waste developer which can no longer be used.
A description is provided below of the operation of the aforementioned developer supplying unit for maintaining a constant concentration of developer.
In a first step, enriched developer and carrier are supplied into the developer receptacle from the enriched developer cartridge and the carrier cartridge in a predetermined mixture ratio to form developer with a desired concentration that is most suitable for developing an image (typically about 3% solid). In a second step, the developer is supplied to a photoconductor and then an image is developed in a third, or printing step.
If the concentration of the developer drops below an appropriate value due to continuous or repeated printing operations, the concentration sensor provided for sensing the concentration of the developer in the developer receptacle senses the low concentration and directs the enriched developer of the developer receptacle to be replenished from the enriched developer cartridge, whereby the developer in the developer receptacle can be maintained at a predetermined concentration. If the developer is maintained at an appropriate concentration level while the amount of the developer remaining in the developer receptacle is deficient, the level sensor provided for the developer senses the deficiency of remaining amount of the developer and directs a desired amount of the enriched developer and carrier to be replenished from the enriched developer cartridge and the carrier cartridge, whereby an appropriate amount of the developer can be maintained. In addition, the level sensors provided in the enriched developer and carrier cartridges sense the remaining amount of the enriched developer in the developer cartridge and the remaining amount of the carrier in the carrier cartridge respectively, and inform the user of the sensed results. Then, when required, the user replaces the enriched developer cartridge and/or the carrier cartridge, so that the printing can be continuously performed.
As described above, a wet electrophotographic image forming machine that performs printing using developer is capable of informing a user of the deficiency of developer and replacement timing of an enriched developer cartridge by using respective level sensors. However, with the prior wet electrophotographic image forming machine, it is necessary to also provide a concentration sensor or the like for sensing a concentration of developer because a constant concentration of developer is also desired, as well as providing a separate enriched developer cartridge and carrier cartridge for controlling the concentration of the developer. Accordingly, there is a problem in that the image forming machine is larger and the manufacturing cost thereof increases.
Accordingly, there has been a need for developing a wet electrophotographic image forming machine which is capable of sensing the condition of developer without using a level sensor or a concentration sensor and to externally display the deficiency of developer when the remaining amount or concentration of the developer is deficient.